1. Field of the Invention
The invention relates to a motive power assembly for a vehicle with hybrid motorization equipped with a double planetary gear train.
The invention relates more particularly to a motive power assembly for a vehicle with hybrid motorization functioning in a plurality of modes, of the type equipped with a first planetary gear train provided with elements such as a first annulus, a first planet wheel, a first planet carrier and at least one first planet, linked in rotation to components of the motive power assembly, such as an output shaft of an electric motor, an output shaft of an internal combustion engine, a shaft of the rotor of an alternator and a power output to transmit motive power to the wheels of the vehicle, and of the type in which an electronic module for control of the charge of a battery package actuates, especially as regards torque and speed, the operation of the electric motor and of the alternator, which can be placed under load in particular to recharge the battery package.
2. Discussion of the Background
There are known numerous examples of motive power assemblies for vehicles with hybrid motorization. These fall essentially into two categories, the series hybrid units and the parallel hybrid units.
The series hybrids are motive power assemblies in which a piston-type internal combustion engine or a turbine drives a generator which produces electricity to energize one or more electric motors linked to the wheels of the vehicle. A battery package ensures storage of the electrical energy needed to operate the electric motor.
French Patent FR A 2734318 describes such a motive power assembly.
The efficiency of such a power transmission chain is good, but such a device suffers from the disadvantage of requiring bulky electrical components which lead to excessive on-board weight. The components used must in fact ensure propulsion of the vehicle at all speeds, thus necessitating the use of large-sized components. In addition, the vehicle is immobilized by failure of any one of the electrical components.
The parallel hybrids are motive power assemblies in which an internal combustion engine, an electric motor energized by a battery package and a transmission are mechanically coupled via a device which permits them to be linked in rotation to one another. They are generally devices equipped with a planetary gear train or gearbox, to the elements of which there are connected the electric motor, the internal combustion engine and the transmission.
The motive power assemblies of parallel hybrid type have the advantage that they can use both types of propulsion, internal combustion and electric, independently or simultaneously. Since the two motive units are coupled to one another, the vehicle can, for example, operate in pure electrical mode or in hybrid mode or even in pure internal combustion engine mode, depending on the use conditions, or in other words depending on the desired acceleration, or on where the vehicle is being used or on the speed of the vehicle. The change from one mode of operation to another is actuated by an electronic module.
This device makes it possible to use the motive power of the internal combustion engine directly for vehicle propulsion, while the electric motor has merely a booster function, thus allowing the use exclusively of electrical components of smaller dimensions and weights.
One of the functions assigned to the internal combustion engine is to recharge the battery package via the electric motor, which is then used as a generator. Such a motive power assembly does not require either an electric motor or bulky battery package. In addition, the possibility of using one of the motive units preferentially ensures that the vehicle will not be immobilized if the other motive unit fails. Finally, the mechanical coupling of the components makes it possible to start the internal combustion engine by driving its output shaft by the electric motor instead of doing so in the conventional manner by a starter, thus in turn making it possible to achieve appreciable weight savings and to reduce the production costs.
Other hybrid designs are also known, especially those in which the electric motor and the transmission are coupled to the elements of the planetary gear system and in which an alternator is also coupled mechanically to the planetary gear train for the purpose of recharging the battery package. In this type of configuration the motive power assembly is provided in certain cases with two sources for recharging the battery package, which are the alternator and the electric motor, which is used occasionally as a current generator.
A problem nevertheless arises as regards control of the torque and of the speed of rotation of the different elements.
It is known that an internal combustion engine operates at its best efficiency only at its speed corresponding to maximum torque. In a conventional vehicle propelled by an internal combustion engine, the internal combustion engine is the sole source of power and it is used at different speeds of rotation to achieve different vehicle velocities. In doing so, it operates only rarely at its speed corresponding to maximum torque, since it must give fresh impetus to the vehicle, especially after every gear change.
The problem is different in the case of a hybrid vehicle, where on the one hand the search for low consumption is the predominant concern and on the other hand an electric motor can be used. The premise in this case is to use the internal combustion engine as the power source at constant torque and speed, while the electric motor is capable of supplying the power boost necessary to achieve the desired accelerations.
It is therefore important for the electronic module to be able to perform a regulating action on the torque of the internal combustion engine, in order to permit it to operate at its speed corresponding to maximum torque. A simple solution to this end comprises ensuring fine control of the torques and speeds of the other elements of the hybrid propulsion chain, or in other words the electric motor and alternator, by means of the electronic module.
The problem not resolved by the existing devices results from the architecture comprising a planetary gear train for coupling the elements of the motive power assembly. In fact, since the elements are linked mechanically to one another by the planetary gear train, their torques and speeds of rotation are related to one another by the law of composition of speeds within the planetary gear train. This is advantageous in terms of power transmission but poses a problem when one element is in charge of actuation functions. For example, in the architecture described in the foregoing, the alternator is capable of delivering a resisting torque to one of the elements of the planetary gear train, thus ensuring that the torque from the motive unit is transmitted by engagement of the two other elements of the planetary gear train, especially when the electronic module actuates starting of the internal combustion engine by driving its output shaft. The resisting torque delivered by the alternator is then used for actuation purposes, but it is not used directly for propulsion of the vehicle.
Similarly, when the vehicle is propelled simultaneously by the electric motor and the internal combustion engine, the charged status of the battery package may be sufficient to ensure that operation of the alternator is not required. In this case it is not necessary to drive the alternator, because rotation thereof inevitably causes mechanical losses.
Finally, the limited number of three power inputs or outputs of a planetary gear train inevitably requires the mechanical coupling of two components of the motive power assembly to a single element of the planetary gear train, which coupling is generally achieved by connecting the electric motor to the bridge via one of the elements of the planetary gear train. In such a configuration, the mode of recharging of the battery package of the vehicle at standstill can be achieved only by means of the alternator, thus greatly prolonging the charging time. If the capability of using the electric motor as a current generator is desired, it is important that this motor can be disconnected from the bridge.
To meet these imperative criteria of decoupling of the components, the invention proposes a motive power assembly of the type mentioned hereinabove, characterized in that the motive power assembly is equipped with a second planetary gear train which is provided with elements such as a second annulus, a second planet wheel, a second planet carrier and at least one second planet, one of which is linked in rotation to the output shaft of the electric motor and the others of which are linked to the power output of the first planetary gear train and to the bridge in order to transmit the motive power to the wheels of the vehicle, and in that the electronic module actuates the operation of the internal combustion engine and the means for locking the output shaft of the internal combustion engine.
According to other characteristics of the invention:
the means for locking the output shaft of the internal combustion engine are provided with a brake functioning in active locking mode or in inactive mode on an engine flywheel linked in rotation to the output shaft of the internal combustion engine;
the first planetary gear train is coaxial with the second planetary gear train, the first planet carrier is linked in rotation to the second planet wheel and the first annulus is linked in rotation to the second annulus;
the first annulus and the second annulus form a common annulus, and in that the first planet carrier and the second planet wheel form a common hub;
the annulus common to the two planetary gear trains is linked in rotation to the output shaft of the electric motor, the first planet wheel is linked in rotation to the shaft of the alternator rotor, the common hub is linked in rotation to the output shaft of the internal combustion engine, and the second planet carrier is linked in rotation to the wheels of the vehicle;
the electronic module is capable of actuating a pure electrical mode of operation in which the brake of the engine flywheel is active and the alternator is not under load;
the electronic module is capable of actuating a mode of operation of starting of the internal combustion engine by the electric motor, in which mode the brake of the engine flywheel is inactive and the alternator is under load;
the electronic module is capable of actuating a free hybrid mode of operation in which both motive units are running, the brake of the engine flywheel is inactive and the alternator is under load;
the electronic module is capable of actuating, when the vehicle is at standstill, a mode of operation of recharging of the battery package, in which mode the internal combustion engine is running and the brake of the engine flywheel is inactive, the alternator is under load and the electric motor is used as a current generator;
the motive power assembly is provided with a brake for locking the shaft of the alternator rotor, which brake can be actuated in an active locking mode or in an inactive mode by the electronic module;
the electronic module is capable of actuating a locked hybrid mode of operation in which both motive units are running, the brake of the engine flywheel is inactive, the brake of the shaft of the alternator rotor is active and the alternator is under load;
the linking in rotation of the output shaft of the electric motor to the annulus and the linking in rotation of the second planet carrier to the bridge are achieved via transmission components such as serrated belts or chains;
the motive power assembly is provided with a common case, which accommodates the two planetary gear trains, the transmission components, a bridge, on which there are fixed the electric motor, the alternator and the internal combustion engine.